This invention relates to thermoplastic resin compositions which are mainly composed of polyarylate resins, polyamide resins and epoxy resins and have excellent impact strength, heat and solvent resistances and moldability.
Compositions made of polyarylate resins and polyamide resins have good heat and solvent resistances and good moldability. For instance, Japanese Patent Publication No. 56-14699 discloses a resin composition made of a polyarylate and a polyamide, and Japanese Laid-open Patent Application No. 52-100552 discloses a resin composition which is made of a polyarylate-based resin composed of a mixture of a polyarylate and polyethylene terephthalate, and a polyamide.
Since polyarylates and polyamides are substantially immiscible with each other, the composition obtained by melt kneading exhibits a phase separation structure wherein the adhesion strength at the interface between the polyarylate phase and the polyamide phase is weak, with the attendant disadvantage of the resulting composition that the impact strength becomes small, thus leading to brittleness.
Attempts have been made to improve the impact strength of the resin compositions made of polyarylates and polyamides by addition, as the third ingredient, of a miscibility improver or an impact strength improver. For instance, in Japanese Laid-open Patent Application, there is used an N-substituted amido-containing polymer as the third ingredient. As the third ingredient, there are used polyalkylene phenylene esters containing a group of sulfonate salt in Japanese Laid-open Patent Application No. 59-105050, glycidyl group-containing olefin copolymers in Japanese Laid-open Patent Application No. 61-183353, mixtures of epoxy group-containing ethylene copolymers and acid anhydride-containing olefin copolymer in Japanese Laid-open Patent Application Nos. 62-277462 and 62-283146.
However, the resin compositions disclosed in the Japanese Laid-open Patent Application Nos. 58-67749 and 59-105050 are far from satisfactory in improving the impact strength. With the resin compositions disclosed in the Japanese Laid-open Patent Application Nos. 61-183353, 62-277462 and 62-283146, the effect of improving the impact strength starts to develop when the content of the third ingredient exceeds about 5 wt %. For obtaining satisfactory impact strength, the third ingredient has to be added in amount ranging from 10 to 30 wt %. Such resin compositions are unfavorably apt to undergo thermal decomposition in the cylinder of an extruder or injection molding machine, with attendant disadvantages such as gelation, coloration, a lowering of mechanical strength, and defects in appearance of the resultant moldings such as flow mark, silver streak and silver blister. Moreover, since olefin polymers are formulated in large amounts, the resulting resin compositions is improved in the impact strength but is considerably lowered with respect to the tensile strength, bending strength, modulus of elasticity and heat resistance.
A resin compositions made of a polyarylate resin, a polyethylene terephthalate resin and a polyamide resin has excellent heat and solvent resistances and moldability and is disclosed, for example, in Japanese Patent Publication No. 58-50260. However, this resin composition has such problems as involved in the compositions made of polyarylate resins and polyamide resins. More particularly, although polyarylates and polyethylene terephthalate are miscible with each other, polyamide is incompatible with these resins. The composition obtained by melt kneading of these resins exhibits a phase separation structure wherein the adhesion strength at the interface between the polyarylate and polyethylene terephthalate phases and the polyamide phase is weak, so that the composition has a low impact strength and is brittle.
In order to improve the impact strength of the above composition, Japanese Laid-open Patent Application No. 52-100552 proposed an improved process, but satisfactory mechanical strength has not yet been obtained.
Japanese Patent Public Disclosure No. 187761/1987 discloses a thermoplastic resin composition comprising polycarbonate, poly(ester carbonate) and polyamide, in which bisphenol A diglycidyl ether is contained as a compatibilizer having an epoxy group.
However, the composition disclosed in Japanese Patent Public Disclosure No. 187761/1987 is chiefly composed of polycarbonate. Polycarbonate is decomposed easily by heat in the presence of even a small quantity of basic substance. In kneading of polycarbonate and polyamide, therefore, polycarbonate is decomposed during thermal melting caused by the amide bond and terminal amino group of polyamide. In addition, since a monomer such as bisphenol A diglycidyl ether is used as the compatibilizer, it is difficult to knead such a liquid monomer with resins which are solid at normal temperatures.